shape of p8 tongue (deep curve) is different to the typically flatter curve of cachinnans like here: http://www.lou.bertalan.de/gulls/pic/hi/up_0757.jpg
or like here: http://www.lou.bertalan.de/gulls/pic/vh/up_1430.jpg
but can such a bird identified with certainty, without its outer 2 primaries?
it legs however are very yellow, bill is rel. short but not decisive, in my opinion.